New answers tagged

1

Eddy currents. Conductors resist changes in magnetic field. This is the basis of the magnet-in-copper-pipe demo. When the conductive metal encroaches on the plasma ball it encounters the ball's (spheromak's) magnetic field. The eddy current effect pushes back on the metal and pushes inward on the plasma, compressing and adiabatically heating it. The plasma'...


0

Definitions Let us first start with some definitions of parameters, in no particular order. I will be describing elastic collisions, assuming a quasi-neutral (i.e., $n_{e} = \sum_{s} \ n_{s} \ Z_{s}$) plasma. Thus, the collisions involve long-range forces and are called Coulomb collisions. Constants $e$ = the elementary charge $\varepsilon_{o}$ = the ...


1

If you put your itty bitty magnet with the 1.4 tesla field at the North Magnetic Pole, and another identical one at the South Magnetic Pole, then you would have added 1.4 tesla at each pole. There would be zero effect on the Earth's magnetic field. Like all fields you're likely to encounter, magnetic field strength depends on the distance from the source. ...


0

How strong is Earths magnetic field in space? At what distance? The Earth's magnetic field is roughly modeled as a tilted dipole (i.e., the magnetization axis is tilted with respect to the spin axis of rotation). The magnitude at the magnetic equator is given by the approximation: $$ \lvert \mathbf{B} \rvert \left( r \right) \approx B_{o} \left( \frac{R_{...


5

The ash is removed by the divertor. Since everything in the ring is ionised you can selectively remove ions with a magnetic field using their charge to mas ratio. This is done by the divertor, which pulls out heavier ions while leaving the tritium and deuterium in the ring. As for fuelling, that's basically easy as you don't need to inject much fuel since ...


2

First, I am going to provide a little background on equivalent pressures at different altitudes from Earth's surface. Layers of Earth's Atmosphere Troposphere to Mesosphere At sea level, the neutral atmosphere of Earth has a pressure of ~$10^{5}$ Pa (or ~1000 mbars). The below image from https://en.wikipedia.org/wiki/File:...


3

You are probably referring to a Carrington Event where a large coronal mass ejection from the sun hits the Earth and creates massive disturbances in the magnetic field, with the result that things like the power grid are damaged by the induced currents. On July 23, 2012 a "Carrington-class" Solar Superstorm (Solar flare, Coronal mass ejection, Solar ...


0

In this PDF on page 5 the author explains that a particle moving through a space-charge (electron density in a plasma) gains only thermal energy. After a little more digging, I think I found to what you refer (which is actually on page 3). The plasma oscillations to which the author refers are known as Langmuir waves. In freshman physics, you probably ...


2

Would it be like in gas p/T dependence ? No, it is much more complicated than this. How does the refractive index of plasma changes with temperature? This is an extremely complicated question for numerous nuanced reasons, including (in no particular order): Plasmas are often in a collisionless or weakly collisional state, meaning their dynamics are ...


3

The refractive index comes, mostly, from the electric polarizability of the medium: that is, the amount of electric dipole induced in the medium by a unit driving electric field. This is a macroscopic quantity, calculated by adding up the contributions of each microscopic components, and if you have multiple species in the medium (such as neutral atoms and ...


1

There is no such thing as refractive index of electrons or ions. Although @honeste_vivere has given a very detailed answer but I am answering again thinking that his answer is too much for you. When the electromagnetic radiation interact with plasma the electrons respond quickly and ions are too slow. The plasma refractive index is $$n=\sqrt{\left(1-\frac{...


3

Cold Plasma Index of Refraction We start by deriving the expression for the dielectric tensor, as shown at http://physics.stackexchange.com/a/138460/59023. If we consider the case of a cold uniform plasma with only linear waves, then one can show the dielectric tensor has the form: $$ \begin{align} \overleftrightarrow{\mathbf{K}} & = \left[ \begin{...



Top 50 recent answers are included